This assignment is for ETC5521 Assignment 1 by Team Possum comprising of Brenwin Ang and Joyce Lee.

Introduction and motivation

Volcanoes are nature’s explosive land forms and yet one of the most beautiful. We chanced upon data set released by TidyTuesday which is probably one of if not the most comprehensive data set to learn more about volcanoes.

Volcanoes date back to hundreds and thousands of years ago. This data exploration takes a closer look at the more recent active volcanoes around.

We start with a brief introduction into the world of volcanoes, then visit the interaction between volcano & humans and finally looking into the characteristics of volcano.

Data description

The data source is from The Smithsonian Institution. The data is available, and cleaned, downloadable from tidytuesday github. Cleaning script is also supplied.

Data provided contains 5 linked data sets, each with looking at a particular aspect of volcano:

Analysis and findings

World Of Active Volcanoes

World Map of Active Volcanoes erupt

There are 3 main types of Active Volcanoes (erupted before) namely Stratovolcano, Caldera and Shield. We decided to label the others as others. Stratovolcanoes are by far the most active volcano.

We then plotted the world map of Active Volcanoes with tectonic plate boundaries overlaid.

We found that most of the volcanoes lie along the Pacific Ocean tracing the boundaries of tectonic plates. We later found that was dubbed the Ring of Fire(or Circum-Pacific Belt) . This path is approximately 40,000km long and holds 75% of the World’s Volcanoes are situated and 90% of active ones! The abundance of volcanoes are explained by significant tectonic plates in the area since volcanoes are formed by either converging or diverging tectonic plate boundaries, creating cracks in earth.

To achieve the map, we could not just plot the tectonic boundaries as the polygons stretch across the world map (looking like they are at opposite ends of the world when in fact they are side by side since the globe is round while ggplot is 2D). So, we split the tectonic plates at the prime meridian (x-intercept where long = 0) - was assisted by a helpful member at StackOverflow

This map zoomed into the Ring Of Fire showing volcanoes running along the boundaries. As we can see, the volcanoes here are has more eruptions relatively speaking.

The interaction between volcanoes and humans - How worried should you be about volcanoes?

Population around volcanoes’ vicinity

Above, the height of the triangle/volcanoes corresponds to the number of volcanoes within one of the six population category that is within 5km, 10km, 30km and 100km from the volcano respectively. give better explation

There is no fixed safety risk zones(or distnace) as volcanoes are unpredictable. However, it is said around 1km for small/medium sized eruptions(VEI = 1-2) is relatively safe as long as volcanic projectiles do not fall in that area. Given this, most volcanoes are less than 5km from a population of people. Above figure was inspired by Sil Aarts’ visualization.

World map with number of eruptions in each country

Above shows plot with fill depending on the number of eruptions in each country and larger dot sizes represent the number of population in the vicinity.

How likely will a volcano erupting in each VEI category after 1812?

VEI measures the explosiveness of volcanic eruptions. It is determined by the volume of materials thrown out(e.g. pyroclastic flow like smoke, ash etc.), eruption cloud height and qualitative observations. As qualitatlively described using terms ranging from “gentle” to “mega-colossal” [Wikipedia]. For example, VEI of 0 given for non-explosive eruptions (\(<10,000m^3\) of fragmental material produced by eruption called tephra). While VEI of 8 can eject \(1\times10^12m^3\) of tephra.

Theoretically, VEI is ranges from 0 to infinity. VEI scaled is on a log scale. Therefore each interval (increase of 1 in VEI) indicate an eruption 10x more powerful. Looking back at the last 132 million years, there were only 40 eruptions documented with VEI-8 magnitude and 10 eruptions of VEI-7 in last 10,000 years.

We filtered the data set to after 1812 where the last observed VEI 7 was recorded at Mount Tambora.

The density plots above shows that likelihood of a VEI 4 and above is very unlikely (less than 1%). In fact, almost 98% of all volcanoes have less than VEI-3.

How Frequent does volcanoes erupt?

The tiles above plot the frequency of the Most Active Volcano in each VEI Category. Each tile represents an eruption.

References